I injected the stable isotope carbon-13 carbon dioxide gas.

我往他们的袋子中注射了 含有稳定性同位素碳13的二氧化碳。

And it turns out nitrogen atoms can have either seven or eight neutrons and remain stable—so nitrogen has what chemists call two stable isotopes.

氮原子可以有7到8个，某些氮原子比另一些氮原子拥有更多的中子，保持稳定的中子。因此氮原子含有化学家所说的两种稳定同位素。

No element heavier than lead (number 82) has a stable isotope, and above number 92 (uranium) lifetimes are so short that these substances are almost non-existent in nature.

比铅（82号）更重的元素都没有稳定的同位素，在铀（92号）之后的元素寿命太短，以致于在自然界中几乎不存在。